async function testSync() {
  const response = await new Promise(resolve => {
    setTimeout(() => {
      resolve("async await test...");
    }, 1000);
  });
  console.log(response);
}
testSync(); //async await test...



function theFileReader(file) {
  return new Promise(function(resolve, reject) {
    let reader = new FileReader()
    reader.readAsArrayBuffer(file)
    reader.onload = function() {
      resolve(this.result);
    }
    reader.onerror = reject;
  })
}

// @param {string} img 图片的base64
// @param {int} dir exif获取的方向信息
// @param {function} next 回调方法，返回校正方向后的base64
var getImgData = function(img, dir, next) {
  // console.log('zheshi img>>', img);
  // console.log('zheshi dir>>', dir);
  // console.log('zheshi next>>', next);

  var image = new Image();
  image.onload = function() {
    var degree = 0,
      drawWidth, drawHeight, width, height;
    drawWidth = this.naturalWidth;
    drawHeight = this.naturalHeight;
    //以下改变一下图片大小
    var maxSide = Math.max(drawWidth, drawHeight);
    if (maxSide > 512) {
      var minSide = Math.min(drawWidth, drawHeight);
      minSide = minSide / maxSide * 512;
      maxSide = 512;
      if (drawWidth > drawHeight) {
        drawWidth = maxSide;
        drawHeight = minSide;
      } else {
        drawWidth = minSide;
        drawHeight = maxSide;
      }
    }
    var canvas = document.createElement('canvas');
    canvas.width = width = drawWidth;
    canvas.height = height = drawHeight;
    var context = canvas.getContext('2d');
    //判断图片方向，重置canvas大小，确定旋转角度，iphone默认的是home键在右方的横屏拍摄方式
    switch (dir) {
      //iphone横屏拍摄，此时home键在左侧 旋转180度
      case 3:
        degree = 180;
        drawWidth = -width;
        drawHeight = -height;
        break;
        //iphone竖屏拍摄，此时home键在下方(正常拿手机的方向) 顺时针90度
      case 6:
        canvas.width = height;
        canvas.height = width;
        degree = 90;
        drawWidth = width;
        drawHeight = -height;
        break;
        //iphone竖屏拍摄，此时home键在上方 逆时针90度
      case 8:
        canvas.width = height;
        canvas.height = width;
        degree = 270;
        drawWidth = -width;
        drawHeight = height;
        break;
    }
    //使用canvas旋转校正
    context.rotate(degree * Math.PI / 180);
    context.drawImage(this, 0, 0, drawWidth, drawHeight);
    //返回校正图片
    next(canvas.toDataURL("image/jpeg", .8));
  }
  image.src = img;
}


export { rotateImg };